The present invention relates to a seal arrangement for a mid turbine frame of a gas turbine, especially an aircraft gas turbine, with a tubular fluid duct, especially an oil duct, which extends along an axial direction, a bearing sleeve surrounding the fluid duct radially outside and in the peripheral direction, and at least one seal ring arranged between fluid duct and bearing sleeve in the radial direction, this seal ring being arranged around the fluid duct. By the axial direction is meant here the principal direction of extension of the fluid duct.
In a mid turbine frame, oil ducts are led through struts in order to supply a bearing, the struts extending through an annular channel which conveys hot gas. These ducts comprise a so-called fixed bearing and a so-called floating bearing. The floating bearing of the ducts is designed so that movements in the axial direction of the tubular ducts are permitted during operation of the gas turbine. In the region of the floating bearing, the sealing is produced by way of a piston ring, which is provided on the outside of the duct, especially in a groove arranged on the duct. This piston ring of rather small dimension in the axial direction of the duct not only provides sealing, but also transmits forces during operation orthogonally to the axial direction of the tubular ducts. In this process, wear may occur between piston ring, duct, and external retainer, called here the bearing sleeve. In particular, fretting may occur at the contact sites between piston ring, duct, and bearing sleeve during operation of the gas turbine when the oil ducts and/or the piston ring itself, being generally designed as a slit ring, begin to vibrate.